Science

Maxwell Peptoids Active Against Herpes Simplex 1 (HSV-1)

Posted on May 18th, 2020

Herpes simplex virus-1 (HSV-1) is an enveloped, double stranded, DNA virus that is transmitted via human to human contact, infecting a majority of people <50 years old worldwide [1]. Symptomatic patients have painful, recurrent, oral lesions. HSV-1 can also infect the eyes and is a leading cause of corneal infectious blindness in developed countries [2]. Currently, there is no cure for HSV-1 infections and those afflicted remain so for life.

Human Cathelicidin Antimicrobial Peptides, or more simply “LL-37”, are found in human white blood cells and help the body attack viruses. Maxwell’s peptoids mimic the structure and other functional characteristics of LL-37. These drug candidates have a well-published history of broad spectrum anti-infectives activity in high-impact journals.

Maxwell Peptoids are biomimetic, synthetic foldamers that have amino acid side chains attached at the nitrogen, instead of at the carbon. This design makes our peptoids resistant to the protease enzymes which many pathogens use to destroy carbon-based immune peptides.

To determine the in vitro activity of Maxwell Peptoids™ against HSV-1, Professor Diamond’s Lab (University Of Louisville) incubated purified virus with Maxwell’s Peptoids ™ for 2 hours at 37oC before infecting cultured oral epithelial cells (OKF6/TERT-1). This human cell assay is a robust model for HSV-1 oral infections. After 24 hours in culture, Professor Diamond’s Lab measured the amount of HSV-1 DNA in the cells, by Quantitative PCR. 5 of the 9 peptoids tested showed promising activity versus control. The results showed a reduction in intracellular HSV-1 viral load indicating that the peptoid mechanism of action is direct and virucidal.

Maxwell Peptoids™ from the initial screening experiment were further evaluated for A) dose dependency and B) time dependency (figure 1). The results show strong virucidal activity, comparable to the naturally occurring LL-37. When the peptoids were added to the OKF6/TERT-1 cultured cells alone, minimal cytotoxicity was observed, demonstrating potential for a safety margin in vivo.

More research is underway to specifically define the mechanism of action, however these results clearly indicate that these peptoids are stable, effective antiviral agents able to treat and/or prevent HSV-1 infections.

References:

1- World Health Organization. (2015, October 25). Globally, an estimated two-thirds of the
population under 50 are infected with herpes simplex virus type 1.
https://www.who.int/news-room/detail/28-10-2015-globally-an-estimated-two-thirds-of-the-population-under-50-are-infected-with-herpes-simplex-virus-type-1

Antiviral Human Antimicrobial Peptides

Posted on April 20th, 2020

Maxwell’s Peptoid drug class is designed to mimic an antimicrobial peptide used in the innate human immune system known as human cathelicidin antimicrobial peptide (hCAMP-18), hCAP18, or more simply LL-37. Although there are multiple cathelicidins found in nature, humans only express this single cathelicidin: LL-37. The biomimicry of Maxwell’s drug class includes LL-37’s functional hylical structure, the molecule’s folding properties, the amphipathic (use of both positive and negative charges) properties, and many of the mechanisms of action. This is a review of the published scientific studies showing the multiple mechanisms of action exhibited by natural immune peptides.

Natural immune peptides are amazingly broad-acting against every studied pathogen. However, they do not make optimal therapeutic drugs because they degrade too quickly inside the body (6 minutes). Maxwell’s peptoid drugs mimic the anti-infective qualities of natural peptides, while resisting degradation, allowing the Maxwell peptoids to continue to act on pathogens for at least 24 hours. [In Vivo Biodistribution and Small Animal PET of 64Cu Labeled Antimicrobial Peptoids, 2012]

Representative decay-corrected coronal small-animal positron emission tomography (PET) scan – an imaging test that helps reveal how tissues and organs are functioning and how a drug moves through the body. A PET scan uses a radioactive drug (tracer) to show this activity. These PET images of Balb/c mice are taken at different time points after administration with a Maxwell peptoid that has been tagged with a mildly radioactive form of copper (64Cu-1). The isotope-tagged molecule was administered through interperitoneal injection (A “IP”), oral chow (B “OP”), and intravenous injection (C “IV”) (n=4 for each group).

Multiple Mechanisms of Action

Maxwell’s scientists have studied peptoid mechanisms of action using electron microscopy photographs of membrane disruption. Our studies show that Maxwell’s peptoids attach to membranes with very similar mechanisms to LL-37. That said, identical properties cannot be assumed. We can use these LL-37 studies as a guide post for further study of peptoid mechanism of action.

LL-37 attaches to the membranes of pathogens, opens holes in the membranes, and then acts on the internal contents to bind the DNA and RNA, irreversibly inactivating the functional portions of the pathogen. Below is an image from a study published in Nature (2005) which shows LL-37’s mechanism of action against a membrane (illustrations A, B, C) and against nucleic acids, proteins and other internal structures (illustration D).

Reproduced with permission. Copyright 2005, Nature.
Illustrated above are multiple mechanisms of action in which natural immune peptides attach to and disrupt the negatively charged outer membrane of a pathogen (A-C), and how natural peptides attack the inner workings of a pathogen (D). These mechanisms of action have been evidenced extensively in peer-reviewed publications, for Maxwell’s drug as well as the LL-37 peptide using multiple forms of imaging.

Assessing the interaction of antimicrobial peptides with phospholipids in model membranes provides some insight into their mechanisms of activity. The attraction, attachment, insertion and orientation of the peptide in the lipid bilayer can be determined by X-ray crystallography, NMR spectroscopy in solution and in the presence of lipid bilayers, and FTIR, Raman, fluorescence and CD optical spectroscopies.
[Brogden, K. Antimicrobial peptides: pore formers or metabolic inhibitors in bacteria?. Nat Rev Microbiol 3, 238–250 (2005).]

Dr Annelise Barron et al present data in Nature, Scientific Reports (2017) demonstrating that peptoids (like natural immune peptides) are “fast killers”, which rapidly act inside the external membrane to attack and bind inner structures in vitro and in vivo such as proteins, DNA and RNA. Barron et al. suggest intracellular biomass flocculation as a key mechanism of killing. This process has a similar outcome to injecting glue into the gears of a complex machine. This novel flocculation mechanism of action may explain why peptoids require low concentrations (micromolar) for activity, show significant selectivity for killing negatively charged pathogens over mammalian cells, and finally, why development of resistance to Maxwell’s peptoids is less prevalent than developed resistance to conventional drugs.
[Chongsiriwatana, N.P., Lin, J.S., Kapoor, R. et al.Intracellular biomass flocculation as a key mechanism of rapid bacterial killing by cationic, amphipathic antimicrobial peptides and peptoids. Sci Rep7, 16718 (2017).]

Introduction to Antiviral Activity of Human Cathelicidin (LL-37)

Cathelicidins are a fundamental component of the innate immune system and play a vital role in the initial immune response generated against both injury and infections. Cathelicidin immune response is rapidly activated at the first stage of immune defense against infections. LL-37 is primarily synthesized and stored in cells of myeloid origin and epithelial cells, among the first responders to infections. LL-37 is expressed in a wide variety of tissues including skin, eyes, oral cavity, ears, airway, lung, female reproductive tract, cervical-vaginal fluid, intestines, and urinary tract [1,2].
Ahmed et al. in Human Antimicrobial Peptides as Therapeutics for Viral Infections, a review of relevant literature published in Viruses, 2019.

Viruses

LL-37 has been studied for its activity against the viruses listed below, primarily observed in the peptide’s direct interaction with the outer envelope membrane. New studies are reporting that LL-37 binds proteins contained within the envelope, and several have observed LL-37 irreversibly binding RNA and DNA.

Influenza A Virus (IAV)

As shown in the illustration, Influenza is a negatively charged nano particle. Contained within the outer envelope is a capsid, which contains the RNA virus which the virus uses to replace human RNA and replicate itself inside of a human cell.

LL-37 therapeutic activity against influenza type A virus has been demonstrated in vivo and in vitro. It is likely that in vivo, IAV encounters LL-37 in the respiratory tract following innate immune responses against the virus and is secreted from neutrophils, macrophages, and epithelial cells [44 ,49 ].Early studies assessed the antiviral activity of LL-37 in vivo using a mouse IAV strain [50 ]. Mice were nebulized with LL-37 (500 g/ mL) a day prior to infection with a lethal dose of IVA PR/ 8 mouse strain, and survival and weight loss were monitored for 14 days following infection [50 ]. Initially, all mice exhibited weight loss, but weight loss ceased at day seven in mice treated with LL-37 or the IAV antiviral zanamivir. Mice treated with LL-37 and zanamivir exhibited 60% survival compared to the untreated group which succumbed to infection by day 9. This suggests that therapeutic use of LL-37 reduces IAV infection severity in a manner comparable to zanamivir [50 ]. LL-37 also decreased expression of inflammatory cytokines, particularly IL-1 , granulocyte-macrophage colony-stimulating factor (GM-CSF), keratinocytes chemoattractant (KC), and the chemotactic cytokine known as regulated on activation normal t-cell expressed and secreted (RANTES), in bronchoalveolar lavage fluid in mice infected with PR/ 8 two days following LL-37 treatment as determined by immunoassay demonstrating the immunomodulatory properties of LL-37 [50]. In vitro plaque assays demonstrated one log inhibition of PR/ 8 when virus was pre-incubated with LL-37 (50 g/ mL) in Madin-Darby canine kidney (MDCK) cells [50].[Ahmed et al, 2019]

Human Immunodeficiency Virus (HIV)

Earlier studies provided evidence of LL-37’s ability to protect against HIV-1 infection given epithelial expression of LL-37, including in peripheral blood mononuclear cells such as CD4+T-cells in vitro [52 ]. LL-37 directly inhibits the activity of HIV-1 reverse transcriptase via a protein–protein interaction in a dose-dependent manner (IC50 =15 M) [9 ,53 ]. Inhibition of HIV-1 protease activity with LL-37 has also been reported; however, this activity is less potent when compared to inhibition of HIV-1 reverse transcriptase (20%–30% inhibition at 100 M). In addition, the plasma levels of LL-37 in HIV positive individuals undergoing antiretroviral therapy (ART) are much higher than in patients who are not, corresponding with an increased susceptibility to secondary infections in patients not undergoing ART [54].[Ahmed et al, 2019]

Respiratory Syncytial Virus (RSV)

Respiratory syncytial (sin-SISH-uhl) virus, or RSV, is a common respiratory virus that usually causes mild, cold-like symptoms. Most people recover in a week or two, but RSV can be serious, especially for infants and older adults. In fact, RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia (infection of the lungs) in children younger than 1 year of age in the United States. It is also a significant cause of respiratory illness in older adults. [Centers for Disease Control website, 30 March 2020)

A few studies have demonstrated the efficacy of LL-37 against RSV [11 ,57 ]. Cells pre-incubated with LL-37 (> 10 g/ mL) are protected against RSV infection whereas addition of LL-37 two hours post-infection results in decreased antiviral activity [57 ]. Additionally, LL-37 can limit viral-induced cell death in infected cell cultures, indicating that the peptide’s activity is not limited to prophylactic treatment. Treatment of epithelial cells with LL-37 prior to infection results in peptide internalization and retention, which provides antiviral protection for several hours post-treatment [57 ]. Furthermore, RSV infection induces the production of cytokines and chemokines in lungs. LL-37 (50 g/ mL) can impact the expression of chemokines as well as viral load when pre-incubated with RSV [11 ]. While the exact mechanism of the antiviral activity of LL-37 against RSV is not well established, it is speculated that the peptide directly interacts with the virus prior to infection, due to its dose-dependent early effects on RSV infection. Interestingly, children with lower cathelicidin levels are more susceptible to RSV infection and display an increase in the severity of RSV-associated bronchitis [58 ].[Ahmed et al, 2019]

Human Rhinovirus (HRV)

Human rhinoviruses (HRVs) are causative agents of the common cold and most viral respiratory tract infections. As respiratory epithelial cells are the primary targets of HRV infection, studies evaluating the efficacy of LL-37 on HRV have utilized airway epithelial cells. LL-37 (50 g/ mL) demonstrates direct antiviral activity against HRV when added as a pre-treatment by acting on viral particles, and when added post-infection by acting on the host cell [59 ]. LL-37 can induce a significant reduction in the metabolic activity of infected cells, as measured by mitochondrial metabolic potential [59 ]. Studies evaluating HRV in cystic fibrosis cells have revealed that expression of LL-37 decreases HRV viral load in vivo [60 ]. Thus, LL-37 reduces HRV infections in respiratory cells as well as in cystic fibrosis cells.[Ahmed et al, 2019]

Vaccinia Virus (VACV)

Vaccinia virus (VACV) is a DNA virus that can infect many types of mammalian cells. LL-37 limits VACV replication and can alter viral membranes [61 ]. VACV gene expression and viral titers are reduced in a dose-dependent manner in cells pre-incubated with LL-37 (25–50 M) [61 ]. Transmission electron microscopy images have shown a disruption in the integrity of VACV viral membrane after 24 hour incubation with LL-37. Whereas murine LL-37 has demonstrated great efficacy and protection against VACV during infection, the efficacy of human LL-37 against VACV is unknown [61 ].[Ahmed et al, 2019]

Herpes Simplex Virus (HSV)

Maxwell scientists have studied our peptoid drug candidates against HSV-1 in human mouth epithelial cells and human lung cells. Each cell line showed similar results to the LL-37 studies in human corneal cell line discussed in Ahmed et al, 2019.

Zika Virus (ZIKV)

Zika virus (ZIKV) is a positive-sense, single-stranded RNA virus that can cause fever, headaches, rashes, joint pain, and myalgia in children and adults, and “microcephaly, ventriculomegaly, intracranial calcifications, abnormalities of the corpus callosum, retinal lesions, craniofacial disorder, hearing loss, and dysphagia” in neonates [65 ]. The emergence of ZIKV is a global concern since it is the first major infectious disease that has been associated with birth defects in over five decades [66 ]. Currently, no vaccines or treatments are available to prevent ZIKV infection [66 ]. He et al. [46 ] conducted a study to determine whether LL-37 and synthetic derivatives can be used to treat ZIKV infection in primary human fetal astrocytes [46 ]. Whereas LL-37 is toxic to these cells (EC50 =20 M), an LL-37 derivative, GF-17, can be safely used due to its lower toxicity (EC50 >50 M) [46 ]. Treatment of primary human fetal astrocytes with 10 M of GF-17 24 h after ZIKV infection results in a seven-fold decrease in the number of ZIKV plaque forming units [46 ]. Pre-incubation of ZIKV between 1 and 4 h with GF-17 (10 M), results in at least a 95% decrease in the number of active zika virions [46 ]. In addition to the possibility of GF-17 directly interacting with ZIKV virions as a mechanism of antiviral activity, GF-17 increases interferon- 2 (IFN- 2) expression in a dose-dependent manner, which further impacts the ability of ZIKV to infect primary human fetal astrocytes [46 ].[Ahmed et al, 2019]

Hepatitis C Virus (HCV)

Maxwell’s peptoids have been tested against HCV. Data from the Institute of Infectious Diseases, Tokyo (Japan’s CDC) shows that multiple Peptoid drug candidates are rapidly and remarkably effective against Hepatitis C, which is an RNA virus. It is remarkable because our drugs are also effective against Herpes Simplex Virus 1 which is a DNA virus.

These results are profound in that they show our drug class may be broadly virucidal

Hepatitis is a single strand RNA virus particle similar in structure to Coronavirus

Drugs already exist to the HCV need; therefore, not a commercial target for Maxwell

Venezuelan Equine Encephalitis Virus (VEEV)

Scientists at the National Center for Biodefense and Infectious Disease at George Mason University, tested the host defense peptide LL-37 against VEEV. Their data shows that LL-37 “exhibits robust antiviral activity with minimal toxicity” to humans. Their works appears to show that treatment of the virus with LL-37 appears to block the virus from entering human cells. Additionally, they found that LL-37 enhanced type I interferon (IFN) expression in infected host cells, creating an antiviral state inside the infected cell. LL-37 also inhibited the most virulent strain of VEEV – the Trinidad Donkey (TrD) strain.

Mechanisms of Action

Almost universally, pre-incubation of free virus particles prior to attempted infection of human cells appears to be the most successful strategy for LL-37’s ability to inhibit viral replication. If the virus cannot enter the host cell, then the virus is not able to replicate and is irreversibly inactivated. This has multiple benefits in that it acts rapidly, prevents further cellular damage, and acts on the core cause of host disease pathology, and most importantly eliminates the that inactivated virus permanently.

2) Carpet Model of Viral Envelope Removal

LL-37 is proposed to remove the outer membrane of viruses in a single event rather than gradual piece-by-piece removal. [37] This suggests a carpet model of antimicrobial peptide action, wherein a susceptible membrane remains intact until a threshold concentration of peptide is reached, following which a rapid disintegration of the targeted membrane occurs. [47,48]. [Ahmed et al, 2019]

Removing the outer membrane – removing the viruses mask – exposes the virus to the adaptive immune system, and allows the body to tag the virus with antibodies for removal.

Interestingly, the least effective peptide uperin-3.1 was equally effective as the others at inducing susceptibility to neutralizing antibody. This suggests that in addition to direct killing by a carpet-based mechanism, the peptides may simultaneously operate a different mechanism that exposes sequestered antigen without membrane removal. [47] [Dean, R. E., et al, 2010]

Maxwell’s drug is similar to LL-37 in that they both use an electrostatic mechanism of action: positively charged nanoparticles are attracted to negatively charged nanoparticles. Viral membranes, RNA, and DNA are negatively charged, and therefore are irresistibly attractive to positively charged aspects of LL-37 and Maxwell’s peptoid drugs. Once associated with the membrane of the pathogen, the positively charged elements of the natural peptides and the synthetic peptoids tend to attract other viruses causing the viruses to stick to each other as if glued together – causing immobilization and inactivation via biomass clumping, flocculation or aggregation.

Stanford University’s Dr. Annelise Barron published data in Nature Scientific Reports [Intracellular Biomass Flocculation as a Key Mechanism of Rapid Bacterial Killing by Cationic, Amphipathic Antimicrobial Peptides and Peptoids, 2017] that showed the same mechanism of action occurs in bacteria treated with LL-37 and with Maxwell’s peptoid drugs. This may be applicable to peptoid activity against viruses because the electrostatic elements are very similar, and the bacterial aggregation occurred in internal organelles and structures such as DNA and RNA which are shared with viral structures. In photo A of the image below, it is apparent that the internal distribution of an untreated bacteria shows a relatively uniform distribution of internal systems. In photos E, F, G, H and I, aggregation of RNA, DNA and other internal systems is illustrated using transmission electron microscope imaging.

Maxwell’s new drug class includes multiple drug candidates based on naturally occurring immune peptides, but with side chains appended to backbone nitrogens instead of carbon. The nitrogen bond is stronger than a carbon bond, and these novel peptoid (“peptide-like”) synthetic virucides have been shown to irreversibly inactivate viral DNA at low doses. Early preclinical data also shows safety as a potential therapeutic for humans.

Novel, Patented TechnologyMaxwell’s lead virucidal peptoids are designed to serve as structural, functional, and mechanistic mimics of natural virucidal peptides used by the human immune system to defend against pathogens. This virucidal peptoid class is protected by a granted patent assigned to Maxwell Biosciences by the US Department of Energy and US National Institutes of Health.

We have published the design, characterization, anti-infective activity, and biomimetic mechanisms of synthetic anti-infective peptoids in major peer-reviewed journals. Synthetic virucidal peptoids are synthesized at low cost on a robotic synthesizer and can be scaled up easily, with facile access to high chemical diversity. In their ease of synthesis, peptoids are unique among peptide mimetics. To identify our lead candidates (6mer-13mers), 70 different short synthetic anti-infective peptoids were synthesized, purified, and tested against viruses, 47 different bacterial microorganisms, including wild-type and drug-resistant variants. Many of our anti-infective peptoid drug candidates are as potent as well-known anti-infective drugs currently approved by the FDA (0.4-6.5 µM minimum inhibitory concentrations, MICs). The minimum inhibitory concentration is the smallest amount of a drug necessary to prevent visible growth of the pathogen.

The biomimetic mechanism of action of anti-infective peptoids was shown using a wide range of biophysical tools, including studies of pathogen membranes and DNA, using scanning electron microscopy, transmission electron microscopy, and soft X-ray tomography of untreated vs. treated pathogens. We used super-resolution fluorescence microscopy to show that our lead drug candidates penetrate negatively charged membranes and cause rapid-onset solidification of negatively charged DNA and RNA; this mechanism is identical to that of the human peptide, the cathelicidin LL-37. Due to the mechanism of action, the likelihood of pathogenic resistance emerging to synthetic peptoid candidates may be less than that of conventional drugs, which have more specific molecular targets.

Dr Annelise Barron is the primary inventor and scientific co-founder of Maxwell Biosciences. Below is a list of the publications that have published her work as well as the work of other scientists who are building upon her research using Maxwell’s patented peptoid drug class. This data shows the advantages of using peptoids as broad spectrum anti-infectives and how peptoid anti-infectives mimic antimicrobial peptides.

LL-37 Cathelicidin Antimicrobial Peptide

Posted on October 30th, 2018

LL-37 or Human Cathelicidin Antimicrobial Peptide (CAMP) Background

The cathelicidin family of antimicrobial peptides are found in human and mammalian forms of life, as a mammal’s core tool to fight off microbial invasion of all kinds. The genes associated with the peptides have been thoroughly studied, are well-documented and have been compared between species. Other than a prehensile thumb, one of the most interesting unique aspects of humans is we only have one cathelicidin antimicrobial peptide gene: human gene LL-37.

Unless otherwise stated, the information on this website has not been evaluated by the Food & Drug Administration or any other medical body. As a research organization, we do not diagnose, treat, cure or prevent any illness or disease. Information is shared for educational purposes only. You must consult your doctor before acting on any content on this website, especially if you are pregnant, nursing, taking medication, or have a medical condition.